Incredible stuff, adrenaline, and it more than played its part in the recent clean sweep of England.

In retrospect, it was adrenaline that allowed the All Blacks to put one hand on the 2011 World Cup. It was the miracle hormone that enabled Richie McCaw to get through the tournament on a broken foot.

It also enabled McCaw to play most of the second and all of the third test this month with a broken rib, and Conrad Smith got through much of the action in Dunedin with a broken thumb.

That shouldn't be possible. Courage, bravery and willpower played their part, especially in the case of McCaw, whose capacity to endure pain is extraordinary.

But even McCaw wouldn't be able to get through 80 minutes with a broken rib were it not for the masking powers of adrenaline.

And that's pretty much the only weaponry players have to fight extreme pain. The IRB rules are categoric — painkilling injections on match day are not sanctioned.

McCaw was not drugged to the eyeballs during the World Cup, nor when he ran out to play England in the third test. He'd popped a couple of Panadol. That was it.

As he revealed about the World Cup in his autobiography: "If I have to jump or run or push or tackle, I can do it — adrenaline's a great painkiller. But when play stops and I have to walk or jog to a lineout or scrum 20m away, I'm really struggling.

"I can't walk properly most of the time and I've got to be careful to mask the worst effects of the injury, not just from the media but also from all the people constantly coming and going from the hotel. Not to mention the team and coaches."

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Among his many talents, hiding damaged body parts is another special skill possessed by McCaw. It can't have been easy for him in the last two tests to have given no outward clue that he was in pain.

In the build-up to the All Blacks' second try in Hamilton, McCaw held on to the ball in the midfield, delaying his pass perfectly to Aaron Cruden. The second he let it go, he was hit — hard — by the 126kg Billy Vunipola.

The England No8 smashed into McCaw's ribcage and yet the skipper didn't stay down. He dragged himself back to his feet and played on. It would have hurt enough even without a broken rib. And nor is the skipper alone in getting through test football with damaged parts.

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How did Smith manage to be so good against England when he had an injury that will keep him out for six to eight weeks? He could make thumping tackles on the hulking Manu Tuilagi during the game. Five minutes after the final whistle, though, and the lightest touch on his thumb would have been agonising.